Semi-transparent/transflective lighted interferometric devices

ABSTRACT

In certain embodiments, a device is provided that utilizes both interferometrically reflected light and transmitted light. Light incident on the device is interferometrically reflected from a plurality of layers of the device to emit light in a first direction, the interferometrically reflected light having a first color. Light from a light source is transmitted through the plurality of layers of the device to emit from the device in the first direction, the transmitted light having a second color.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/207,270, filed Sep. 9, 2008, which claims the benefit of U.S.Provisional Application No. 60/994,073, filed Sep. 17, 2007, which isincorporated by reference herein in its entirety.

BACKGROUND

1. Field

The field of the disclosure relates generally to ornamental and imagedisplaying devices utilizing interferometry.

2. Description of the Related Art

Microelectromechanical systems (MEMS) include micro mechanical elements,actuators, and electronics. Micromechanical elements may be createdusing deposition, etching, and/or other micromachining processes thatetch away parts of substrates and/or deposited material layers or thatadd layers to form electrical and electromechanical devices. One type ofMEMS device is called an interferometric modulator. As used herein, theterm interferometric modulator or interferometric light modulator refersto a device that selectively absorbs and/or reflects light using theprinciples of optical interference. In certain embodiments, aninterferometric modulator may comprise a pair of conductive plates, oneor both of which may be transparent and/or reflective in whole or partand capable of relative motion upon application of an appropriateelectrical signal. In a particular embodiment, one plate may comprise astationary layer deposited on a substrate and the other plate maycomprise a metallic membrane separated from the stationary layer by anair gap. As described herein in more detail, the position of one platein relation to another can change the optical interference of lightincident on the interferometric modulator. Such devices have a widerange of applications, and it would be beneficial in the art to utilizeand/or modify the characteristics of these types of devices so thattheir features can be exploited in improving existing products andcreating new products that have not yet been developed.

SUMMARY

In certain embodiments, a device is provided which includes a substratethat is at least partially optically transparent. The device of certainembodiments also includes a first layer over the substrate, wherein thefirst layer is partially optically absorptive, partially opticallyreflective, and partially optically transmissive, and a second layerover the substrate and spaced from the first layer, the first layerlocated between the substrate and the second layer, wherein the secondlayer is partially optically absorptive, partially optically reflective,and partially optically transmissive. The device of certain embodimentsalso includes a light source responsive to a signal and positionedrelative to the substrate such that the first layer and the second layerare located between the substrate and the light source. Light emittedfrom the device in a first direction comprises a first portion of lightincident on the substrate, transmitted through the substrate,transmitted through the first layer, reflected by the second layer,transmitted through the first layer, transmitted through the substrate,and emitted from the substrate in the first direction. The light emittedin the first direction can also include a second portion of lightincident on the substrate, transmitted through the substrate, reflectedby the first layer, transmitted through the substrate, and emitted fromthe substrate in the first direction. In certain embodiments, the lightemitted in the first direction also includes a third portion of lightfrom the light source incident on the second layer, transmitted throughthe second layer, transmitted through the first layer, transmittedthrough the substrate, and emitted from the substrate in the firstdirection.

In certain embodiments a device is provided comprising a first means forpartially absorbing light, partially reflecting light, and partiallytransmitting light and a second means for partially absorbing light,partially reflecting light, and partially transmitting light, the secondmeans spaced from the first means. The device of some embodiments alsoincludes a means for generating light, wherein light emitted from thedevice in a first direction comprises a first portion of light incidenton the first means, transmitted through the first means, reflected bythe second means, transmitted through the first means, and emitted fromthe device in the first direction. The light emitted from the device inthe first direction can also include a second portion of light incidenton the first means, reflected by the first means, and emitted from thedevice in the first direction, and a third portion of light generated bythe light generation means, incident on the second means, transmittedthrough the second means, transmitted through the first means, andemitted from the device in the first direction.

In certain embodiments, a method of displaying an image is provided. Themethod of certain embodiments includes providing a device comprising asubstrate that is at least partially optically transparent. The devicecan also include a first layer over the substrate, wherein the firstlayer is partially optically absorptive, partially opticallytransmissive, and partially optically reflective, and a second layerover the substrate and spaced from the first layer, the first layerlocated between the substrate and the second layer, wherein the secondlayer is partially optically absorptive, partially opticallytransmissive, and partially optically reflective. In certainembodiments, the method includes positioning a light source responsiveto a signal relative to the substrate such that the first layer and thesecond layer are located between the substrate and the light source, andemitting light from the device in a first direction. In certainembodiments, the emitted light comprises a first portion of lightincident on the substrate, transmitted through the substrate,transmitted through the first layer, reflected by the second layer,transmitted through the first layer, transmitted through the substrate,and emitted from the device in the first direction. The emitted lightcan also include a second portion of light incident on the substrate,transmitted through the substrate, reflected by the first layer,transmitted through the substrate, and emitted from the device in thefirst direction. In certain embodiments, the emitted light includes athird portion of light from the light source incident on the secondlayer, transmitted through the second layer, transmitted through thefirst layer, transmitted through the substrate, and emitted from thedevice in the first direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view depicting a portion of one embodiment of aninterferometric modulator display in which a movable reflective layer ofa first interferometric modulator is in a relaxed position and a movablereflective layer of a second interferometric modulator is in an actuatedposition.

FIG. 2 is a system block diagram illustrating one embodiment of anelectronic device incorporating a 3×3 interferometric modulator display.

FIG. 3 is a diagram of movable mirror position versus applied voltagefor one exemplary embodiment of an interferometric modulator of FIG. 1.

FIG. 4 is an illustration of a set of row and column voltages that maybe used to drive an interferometric modulator display.

FIG. 5A illustrates one exemplary frame of display data in the 3×3interferometric modulator display of FIG. 2.

FIG. 5B illustrates one exemplary timing diagram for row and columnsignals that may be used to write the frame of FIG. 5A.

FIGS. 6A and 6B are system block diagrams illustrating an embodiment ofa visual display device comprising a plurality of interferometricmodulators.

FIG. 7A is a cross section of the device of FIG. 1.

FIG. 7B is a cross section of an alternative embodiment of aninterferometric modulator.

FIG. 7C is a cross section of another alternative embodiment of aninterferometric modulator.

FIG. 7D is a cross section of yet another alternative embodiment of aninterferometric modulator.

FIG. 7E is a cross section of an additional alternative embodiment of aninterferometric modulator.

FIG. 8 schematically illustrates an example device in accordance withcertain embodiments described herein.

FIG. 9A schematically illustrates an example device in accordance withcertain embodiments described herein.

FIG. 9B shows the reflectivity of an example device in accordance withcertain embodiments described herein.

FIGS. 9C-9D show CIE chromaticity diagrams of an example device inaccordance with certain embodiments described herein.

FIG. 9E shows a CIE chromaticity diagram of two example devices inaccordance with certain embodiments described herein.

FIG. 9F shows the reflectivity of two example devices in accordance withcertain embodiments described herein.

FIG. 9G shows a CIE chromaticity diagram of two example devices inaccordance with certain embodiments described herein.

FIG. 9H shows the reflectivity of two example devices in accordance withcertain embodiments described herein.

FIG. 10 shows the reflectivity of an example device in accordance withcertain embodiments described herein.

FIG. 11A shows the reflectivity and transmittance of an example devicein accordance with certain embodiments described herein.

FIG. 11B shows a CIE chromaticity diagram of an example device inaccordance with certain embodiments described herein.

FIG. 12A schematically illustrates an example device in accordance withcertain embodiments described herein.

FIG. 12B shows a CIE chromaticity diagram of an example device fordifferent viewing angles in accordance with certain embodimentsdescribed herein.

FIG. 13 shows a CIE chromaticity diagram of an example device fordifferent viewing angles in accordance with certain embodimentsdescribed herein.

FIG. 14A schematically illustrates an example device in accordance withcertain embodiments described herein.

FIGS. 14B-14C show CIE chromaticity diagrams of two example devices inaccordance with certain embodiments described herein.

FIG. 15 schematically illustrates an example device comprising afluorescent material in accordance with certain embodiments describedherein.

FIG. 16 schematically illustrates an example device comprising a thirdlayer in accordance with certain embodiments described herein.

FIG. 17 schematically illustrates another example device comprising athird layer in accordance with certain embodiments described herein.

FIG. 18A schematically illustrates an example device in accordance withcertain embodiments described herein.

FIG. 18B shows the reflectivity of an example device in accordance withcertain embodiments described herein.

FIG. 18C shows a CIE chromaticity diagram of an example device inaccordance with certain embodiments described herein.

FIG. 19 schematically illustrates an example device comprising apassivation layer in accordance with certain embodiments describedherein.

FIG. 20A schematically illustrates an example device in accordance withcertain embodiments described herein.

FIG. 20B shows a CIE chromaticity diagram of example devices inaccordance with certain embodiments described herein.

FIG. 21 schematically illustrates an example device comprising a firstglass layer and a second glass layer in accordance with certainembodiments described herein.

FIG. 22 schematically illustrates an example device having a firstlayer, a second layer, a third layer, and a fourth layer in accordancewith certain embodiments described herein.

FIG. 23 shows the transmittance of an example device in accordance withcertain embodiments described herein.

FIG. 24A schematically illustrates an example device in accordance withcertain embodiments described herein.

FIG. 24B shows the reflectivity of example devices in accordance withcertain embodiments described herein.

FIG. 24C shows a CIE chromaticity diagram of example devices inaccordance with certain embodiments described herein.

FIG. 24D shows the transmittance of example devices in accordance withcertain embodiments described herein.

FIG. 24E shows the reflectivity and transmittance of example devices inaccordance with certain embodiments described herein.

FIG. 24F shows a CIE chromaticity diagram of example devices inaccordance with certain embodiments described herein.

FIGS. 25A-D show CIE chromaticity diagrams of example devices fordifferent viewing angles in accordance with certain embodimentsdescribed herein.

FIG. 26 shows a CIE chromaticity diagram of example devices inaccordance with certain embodiments described herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description is directed to certain specificembodiments. However, the teachings herein can be embodied in amultitude of different ways. In this description, reference is made tothe drawings wherein like parts are designated with like numeralsthroughout. Embodiments described herein may be used in decorative andarchitectural applications such as, for example, for decorative glass.Moreover, and as will be apparent from the following description, theembodiments may be implemented in any device that is configured todisplay an image, whether in motion (e.g., video) or stationary (e.g.,still image), and whether textual or pictorial. More particularly, it iscontemplated that the embodiments may be implemented in or associatedwith a variety of electronic devices such as, but not limited to, mobiletelephones, wireless devices, personal data assistants (PDAs), hand-heldor portable computers, GPS receivers/navigators, cameras, MP3 players,camcorders, game consoles, wrist watches, clocks, calculators,television monitors, flat panel displays, computer monitors, autodisplays (e.g., odometer display, etc.), cockpit controls and/ordisplays, display of camera views (e.g., display of a rear view camerain a vehicle), electronic photographs, electronic billboards or signs,projectors, architectural structures, decorative glass, packaging, andaesthetic structures (e.g., display of images on a piece of jewelry).MEMS devices of similar structure to those described herein can also beused in non-display applications such as in electronic switchingdevices.

In certain embodiments, a display device is provided that utilizes bothinterferometrically reflected light and transmitted light. Lightincident on the display device is interferometrically reflected from aplurality of layers of the display device to emit light in a firstdirection, the interferometrically reflected light having a first color.Light from a light source is transmitted through the plurality of layersof the display device to emit from the display device in the firstdirection, the transmitted light having a second color.

One interferometric modulator display embodiment comprising aninterferometric MEMS display element is illustrated in FIG. 1. In thesedevices, the pixels are in either a bright or dark state. In the bright(“on” or “open”) state, the display element reflects a large portion ofincident visible light to a user. When in the dark (“off” or “closed”)state, the display element reflects little incident visible light to theuser. Depending on the embodiment, the light reflectance properties ofthe “on” and “off” states may be reversed. MEMS pixels can be configuredto reflect predominantly at selected colors, allowing for a colordisplay in addition to black and white.

FIG. 1 is an isometric view depicting two adjacent pixels in a series ofpixels of a visual display, wherein each pixel comprises a MEMSinterferometric modulator. In some embodiments, an interferometricmodulator display comprises a row/column array of these interferometricmodulators. Each interferometric modulator includes a pair of reflectivelayers positioned at a variable and controllable distance from eachother to form a resonant optical gap with at least one variabledimension. In one embodiment, one of the reflective layers may be movedbetween two positions. In the first position, referred to herein as therelaxed position, the movable reflective layer is positioned at arelatively large distance from a fixed partially reflective layer. Inthe second position, referred to herein as the actuated position, themovable reflective layer is positioned more closely adjacent to thepartially reflective layer. Incident light (e.g., visible light) thatreflects from the two layers interferes constructively or destructivelydepending on the position of the movable reflective layer, producingeither an overall reflective or non-reflective state for each pixel.

The depicted portion of the pixel array in FIG. 1 includes two adjacentinterferometric modulators 12 a and 12 b. In the interferometricmodulator 12 a on the left, a movable reflective layer 14 a isillustrated in a relaxed position at a predetermined distance from anoptical stack 16 a, which includes a partially reflective layer. In theinterferometric modulator 12 b on the right, the movable reflectivelayer 14 b is illustrated in an actuated position adjacent to theoptical stack 16 b.

The optical stacks 16 a and 16 b (collectively referred to as opticalstack 16), as referenced herein, typically comprise several fusedlayers, which can include an electrode layer, such as indium tin oxide(ITO), a partially reflective layer, such as chromium, and a transparentdielectric. The optical stack 16 is thus electrically conductive,partially transparent, and partially reflective, and may be fabricated,for example, by depositing one or more of the above layers onto atransparent substrate 20. The partially reflective layer can be formedfrom a variety of materials that are partially reflective such asvarious metals, semiconductors, and dielectrics. The partiallyreflective layer can be formed of one or more layers of materials, andeach of the layers can be formed of a single material or a combinationof materials.

In some embodiments, the layers of the optical stack 16 are patternedinto parallel strips, and may form row electrodes in a display device asdescribed further below. The movable reflective layers 14 a, 14 b may beformed as a series of parallel strips of a deposited metal layer orlayers (orthogonal to the row electrodes of 16 a, 16 b) deposited on topof posts 18 and an intervening sacrificial material deposited betweenthe posts 18. When the sacrificial material is etched away, the movablereflective layers 14 a, 14 b are separated from the optical stacks 16 a,16 b by a defined gap 19. A highly conductive and reflective materialsuch as aluminum may be used for the reflective layers 14 a, 14 b, andthese strips may form column electrodes in a display device. In otherembodiments, layers 14 a, 14 b can be semi-transparent such that thedevice is capable of partially reflecting and partially transmittingvisible light or other non visible wavelengths while retaining theinterferometric properties described herein. In one embodiment, layers14 a, 14 b can comprise transparent material which can providemechanical stability. In certain embodiments, the layers 14 a, 14 bcomprise another layer of a partially reflective material, such asAluminum. In one embodiment, the transparent mechanical layer comprisesa dielectric material, such as Silicon Oxynitride, Silicon Dioxide orSilicon Nitride. In certain embodiments, the transparent mechanicallayer is approximately 1000 to 5000 Angstroms thick and the partiallyreflective layer comprises a highly conductive material, such asAluminum, of approximately 30 to 300 Angstroms thickness. In otherembodiments, the layers 14 a, 14 b are patterned into areas of varyingtransmission and reflectivity. In one embodiment, the variabletransmission and reflectivity is achieved by varying the thickness ofthe reflective material. For example, increasing the thickness cancreate areas of increased reflectivity and decreased transmission.

With no applied voltage, the gap 19 remains between the movablereflective layer 14 a and optical stack 16 a, with the movablereflective layer 14 a in a mechanically relaxed state, as illustrated bythe pixel 12 a in FIG. 1. However, when a potential difference isapplied to a selected row and column, the capacitor formed at theintersection of the row and column electrodes at the corresponding pixelbecomes charged, and electrostatic forces pull the electrodes together.If the voltage is high enough, the movable reflective layer 14 isdeformed and is forced against the optical stack 16. A dielectric layer(not illustrated in this Figure) within the optical stack 16 may preventshorting and control the separation distance between layers 14 and 16,as illustrated by pixel 12 b on the right in FIG. 1. The behavior is thesame regardless of the polarity of the applied potential difference. Inthis way, row/column actuation that can control the reflective vs.non-reflective pixel states is analogous in many ways to that used inconventional LCD and other display technologies.

FIGS. 2 through 5B illustrate one exemplary process and system for usingan array of interferometric modulators in a display application.

FIG. 2 is a system block diagram illustrating one embodiment of anelectronic device that may incorporate certain aspects described herein.In the exemplary embodiment, the electronic device includes a processor21 which may be any general purpose single- or multi-chip microprocessorsuch as an ARM, Pentium®, Pentium II®, Pentium III®, Pentium IV®,Pentium® Pro, an 8051, a MIPS®, a Power PC®, an ALPHA®, or any specialpurpose microprocessor such as a digital signal processor,microcontroller, or a programmable gate array. As is conventional in theart, the processor 21 may be configured to execute one or more softwaremodules. In addition to executing an operating system, the processor maybe configured to execute one or more software applications, including aweb browser, a telephone application, an email program, or any othersoftware application.

In one embodiment, the processor 21 is also configured to communicatewith an array driver 22. In one embodiment, the array driver 22 includesa row driver circuit 24 and a column driver circuit 26 that providesignals to a display array or panel 30. The cross section of the arrayillustrated in FIG. 1 is shown by the lines 1-1 in FIG. 2. For MEMSinterferometric modulators, the row/column actuation protocol may takeadvantage of a hysteresis property of these devices illustrated in FIG.3. It may require, for example, a 10 volt potential difference to causea movable layer to deform from the relaxed state to the actuated state.However, when the voltage is reduced from that value, the movable layermaintains its state as the voltage drops back below 10 volts. In theexemplary embodiment of FIG. 3, the movable layer does not relaxcompletely until the voltage drops below 2 volts. Thus, there exists awindow of applied voltage, about 3 to 7 V in the example illustrated inFIG. 3, within which the device is stable in either the relaxed oractuated state. This is referred to herein as the “hysteresis window” or“stability window.” For a display array having the hysteresischaracteristics of FIG. 3, the row/column actuation protocol can bedesigned such that during row strobing, pixels in the strobed row thatare to be actuated are exposed to a voltage difference of about 10volts, and pixels that are to be relaxed are exposed to a voltagedifference of close to zero volts. After the strobe, the pixels areexposed to a steady state voltage difference of about 5 volts such thatthey remain in whatever state the row strobe put them in. After beingwritten, each pixel sees a potential difference within the “stabilitywindow” of 3-7 volts in this example. This feature makes the pixeldesign illustrated in FIG. 1 stable under the same applied voltageconditions in either an actuated or relaxed pre-existing state. Sinceeach pixel of the interferometric modulator, whether in the actuated orrelaxed state, is essentially a capacitor formed by the fixed and movingreflective layers, this stable state can be held at a voltage within thehysteresis window with almost no power dissipation. Essentially nocurrent flows into the pixel if the applied potential is fixed.

In typical applications, a display frame may be created by asserting theset of column electrodes in accordance with the desired set of actuatedpixels in the first row. A row pulse is then applied to the row 1electrode, actuating the pixels corresponding to the asserted columnlines. The asserted set of column electrodes is then changed tocorrespond to the desired set of actuated pixels in the second row. Apulse is then applied to the row 2 electrode, actuating the appropriatepixels in row 2 in accordance with the asserted column electrodes. Therow 1 pixels are unaffected by the row 2 pulse, and remain in the statethey were set to during the row 1 pulse. This may be repeated for theentire series of rows in a sequential fashion to produce the frame.Generally, the frames are refreshed and/or updated with new display databy continually repeating this process at some desired number of framesper second. A wide variety of protocols for driving row and columnelectrodes of pixel arrays to produce display frames are also well knownand may be used in conjunction with certain embodiments describedherein.

FIGS. 4, 5A, and 5B illustrate one possible actuation protocol forcreating a display frame on the 3×3 array of FIG. 2. FIG. 4 illustratesa possible set of column and row voltage levels that may be used forpixels exhibiting the hysteresis curves of FIG. 3. In the FIG. 4embodiment, actuating a pixel involves setting the appropriate column to−V_(bias), and the appropriate row to +ΔV, which may correspond to −5volts and +5 volts, respectively. Relaxing the pixel is accomplished bysetting the appropriate column to +V_(bias), and the appropriate row tothe same +ΔV, producing a zero volt potential difference across thepixel. In those rows where the row voltage is held at zero volts, thepixels are stable in whatever state they were originally in, regardlessof whether the column is at +V_(bias), or −V_(bias). As is alsoillustrated in FIG. 4, it will be appreciated that voltages of oppositepolarity than those described above can be used, e.g., actuating a pixelcan involve setting the appropriate column to +V_(bias), and theappropriate row to −ΔV. In this embodiment, releasing the pixel isaccomplished by setting the appropriate column to −V_(bias), and theappropriate row to the same −ΔV, producing a zero volt potentialdifference across the pixel.

FIG. 5B is a timing diagram showing a series of row and column signalsapplied to the 3×3 array of FIG. 2 which will result in the displayarrangement illustrated in FIG. 5A, where actuated pixels arenon-reflective. Prior to writing the frame illustrated in FIG. 5A, thepixels can be in any state, and in this example, all the rows are at 0volts, and all the columns are at +5 volts. With these applied voltages,all pixels are stable in their existing actuated or relaxed states.

In the FIG. 5A frame, pixels (1,1), (1,2), (2,2), (3,2) and (3,3) areactuated. To accomplish this, during a “line time” for row 1, columns 1and 2 are set to −5 volts, and column 3 is set to +5 volts. This doesnot change the state of any pixels, because all the pixels remain in the3-7 volt stability window. Row 1 is then strobed with a pulse that goesfrom 0, up to 5 volts, and back to zero. This actuates the (1,1) and(1,2) pixels and relaxes the (1,3) pixel. No other pixels in the arrayare affected. To set row 2 as desired, column 2 is set to −5 volts, andcolumns 1 and 3 are set to +5 volts. The same strobe applied to row 2will then actuate pixel (2,2) and relax pixels (2,1) and (2,3). Again,no other pixels of the array are affected. Row 3 is similarly set bysetting columns 2 and 3 to −5 volts, and column 1 to +5 volts. The row 3strobe sets the row 3 pixels as shown in FIG. 5A. After writing theframe, the row potentials are zero, and the column potentials can remainat either +5 or −5 volts, and the display is then stable in thearrangement of FIG. 5A. It will be appreciated that the same procedurecan be employed for arrays of dozens or hundreds of rows and columns. Itwill also be appreciated that the timing, sequence, and levels ofvoltages used to perform row and column actuation can be varied widelywithin the general principles outlined above, and the above example isexemplary only, and any actuation voltage method can be used with thesystems and methods described herein.

FIGS. 6A and 6B are system block diagrams illustrating an embodiment ofa display device 40. The display device 40 can be, for example, acellular or mobile telephone. However, the same components of displaydevice 40 or slight variations thereof are also illustrative of varioustypes of display devices such as televisions and portable media players.

The display device 40 includes a housing 41, a display 30, an antenna43, a speaker 45, an input device 48, and a microphone 46. The housing41 is generally formed from any of a variety of manufacturing processesas are well known to those of skill in the art, including injectionmolding and vacuum forming. In addition, the housing 41 may be made fromany of a variety of materials, including, but not limited to, plastic,metal, glass, rubber, and ceramic, or a combination thereof. In oneembodiment, the housing 41 includes removable portions (not shown) thatmay be interchanged with other removable portions of different color, orcontaining different logos, pictures, or symbols.

The display 30 of exemplary display device 40 may be any of a variety ofdisplays, including a bi-stable display, as described herein. In otherembodiments, the display 30 includes a flat-panel display, such asplasma, EL, OLED, STN LCD, or TFT LCD as described above, or anon-flat-panel display, such as a CRT or other tube device, as is wellknown to those of skill in the art. However, for purposes of describingthe present embodiment, the display 30 includes an interferometricmodulator display, as described herein.

The components of one embodiment of exemplary display device 40 areschematically illustrated in FIG. 6B. The illustrated exemplary displaydevice 40 includes a housing 41 and can include additional components atleast partially enclosed therein. For example, in one embodiment, theexemplary display device 40 includes a network interface 27 thatincludes an antenna 43, which is coupled to a transceiver 47. Thetransceiver 47 is connected to a processor 21, which is connected toconditioning hardware 52. The conditioning hardware 52 may be configuredto condition a signal (e.g., filter a signal). The conditioning hardware52 is connected to a speaker 45 and a microphone 46. The processor 21 isalso connected to an input device 48 and a driver controller 29. Thedriver controller 29 is coupled to a frame buffer 28 and to an arraydriver 22, which in turn is coupled to a display array 30. A powersupply 50 provides power to all components as required by the particularexemplary display device 40 design.

The network interface 27 includes the antenna 43 and the transceiver 47so that the exemplary display device 40 can communicate with one or moredevices over a network. In one embodiment, the network interface 27 mayalso have some processing capabilities to relieve requirements of theprocessor 21. The antenna 43 is any antenna known to those of skill inthe art for transmitting and receiving signals. In one embodiment, theantenna transmits and receives RF signals according to the IEEE 802.11standard, including IEEE 802.11(a), (b), or (g). In another embodiment,the antenna transmits and receives RF signals according to the BLUETOOTHstandard. In the case of a cellular telephone, the antenna is designedto receive CDMA, GSM, AMPS, or other known signals that are used tocommunicate within a wireless cell phone network. The transceiver 47pre-processes the signals received from the antenna 43 so that they maybe received by and further manipulated by the processor 21. Thetransceiver 47 also processes signals received from the processor 21 sothat they may be transmitted from the exemplary display device 40 viathe antenna 43.

In an alternative embodiment, the transceiver 47 can be replaced by areceiver. In yet another alternative embodiment, network interface 27can be replaced by an image source, which can store or generate imagedata to be sent to the processor 21. For example, the image source canbe a digital video disc (DVD) or a hard-disc drive that contains imagedata, or a software module that generates image data.

Processor 21 generally controls the overall operation of the exemplarydisplay device 40. The processor 21 receives data, such as compressedimage data from the network interface 27 or an image source, andprocesses the data into raw image data or into a format that is readilyprocessed into raw image data. The processor 21 then sends the processeddata to the driver controller 29 or to frame buffer 28 for storage. Rawdata typically refers to the information that identifies the imagecharacteristics at each location within an image. For example, suchimage characteristics can include color, saturation, and gray-scalelevel.

In one embodiment, the processor 21 includes a microcontroller, CPU, orlogic unit to control operation of the exemplary display device 40.Conditioning hardware 52 generally includes amplifiers and filters fortransmitting signals to the speaker 45, and for receiving signals fromthe microphone 46. Conditioning hardware 52 may be discrete componentswithin the exemplary display device 40, or may be incorporated withinthe processor 21 or other components.

The driver controller 29 takes the raw image data generated by theprocessor 21 either directly from the processor 21 or from the framebuffer 28 and reformats the raw image data appropriately for high speedtransmission to the array driver 22. Specifically, the driver controller29 reformats the raw image data into a data flow having a raster-likeformat, such that it has a time order suitable for scanning across thedisplay array 30. Then the driver controller 29 sends the formattedinformation to the array driver 22. Although a driver controller 29,such as a LCD controller, is often associated with the system processor21 as a stand-alone Integrated Circuit (IC), such controllers may beimplemented in many ways. They may be embedded in the processor 21 ashardware, embedded in the processor 21 as software, or fully integratedin hardware with the array driver 22.

Typically, the array driver 22 receives the formatted information fromthe driver controller 29 and reformats the video data into a parallelset of waveforms that are applied many times per second to the hundredsand sometimes thousands of leads coming from the display's x-y matrix ofpixels.

In one embodiment, the driver controller 29, array driver 22, anddisplay array 30 are appropriate for any of the types of displaysdescribed herein. For example, in one embodiment, driver controller 29is a conventional display controller or a bi-stable display controller(e.g., an interferometric modulator controller). In another embodiment,array driver 22 is a conventional driver or a bi-stable display driver(e.g., an interferometric modulator display). In one embodiment, adriver controller 29 is integrated with the array driver 22. Such anembodiment is common in highly integrated systems such as cellularphones, watches, and other small area displays. In yet anotherembodiment, display array 30 is a typical display array or a bi-stabledisplay array (e.g., a display including an array of interferometricmodulators).

The input device 48 allows a user to control the operation of theexemplary display device 40. In one embodiment, input device 48 includesa keypad, such as a QWERTY keyboard or a telephone keypad, a button, aswitch, a touch-sensitive screen, or a pressure- or heat-sensitivemembrane. In one embodiment, the microphone 46 is an input device forthe exemplary display device 40. When the microphone 46 is used to inputdata to the device, voice commands may be provided by a user forcontrolling operations of the exemplary display device 40.

Power supply 50 can include a variety of energy storage devices as arewell known in the art. For example, in one embodiment, power supply 50is a rechargeable battery, such as a nickel-cadmium battery or a lithiumion battery. In another embodiment, power supply 50 is a renewableenergy source, a capacitor, or a solar cell including a plastic solarcell, and solar-cell paint. In another embodiment, power supply 50 isconfigured to receive power from a wall outlet.

In some embodiments, control programmability resides, as describedabove, in a driver controller which can be located in several places inthe electronic display system. In some embodiments, controlprogrammability resides in the array driver 22. Those of skill in theart will recognize that the above-described optimizations may beimplemented in any number of hardware and/or software components and invarious configurations.

The details of the structure of interferometric modulators that operatein accordance with the principles set forth above may vary widely. Forexample, FIGS. 7A-7E illustrate five different embodiments of themovable reflective layer 14 and its supporting structures. FIG. 7A is across section of the embodiment of FIG. 1, where a strip of metalmaterial 14 is deposited on orthogonally extending supports 18. In FIG.7B, the moveable reflective layer 14 is attached to supports at thecorners only, on tethers 32. In FIG. 7C, the moveable reflective layer14 is suspended from a deformable layer 34, which may comprise aflexible metal. The deformable layer 34 connects, directly orindirectly, to the substrate 20 around the perimeter of the deformablelayer 34. These connections are herein referred to as support posts. Theembodiment illustrated in FIG. 7D has support post plugs 42 upon whichthe deformable layer 34 rests. The movable reflective layer 14 remainssuspended over the gap, as in FIGS. 7A-7C, but the deformable layer 34does not form the support posts by filling holes between the deformablelayer 34 and the optical stack 16. Rather, the support posts are formedof a planarization material, which is used to form support post plugs42. The embodiment illustrated in FIG. 7E is based on the embodimentshown in FIG. 7D, but may also be adapted to work with any of theembodiments illustrated in FIGS. 7A-7C, as well as additionalembodiments not shown. In the embodiment shown in FIG. 7E, an extralayer of metal or other conductive material has been used to form a busstructure 44. This allows signal routing along the back of theinterferometric modulators, eliminating a number of electrodes that mayotherwise have had to be formed on the substrate 20.

In embodiments such as those shown in FIG. 7, the interferometricmodulators function as direct-view devices, in which images are viewedfrom the front side of the transparent substrate 20, the side oppositeto that upon which the modulator is arranged. In these embodiments, thereflective layer 14 optically shields the portions of theinterferometric modulator on the side of the reflective layer oppositethe substrate 20, including the deformable layer 34. This allows theshielded areas to be configured and operated upon without negativelyaffecting the image quality. Such shielding allows the bus structure 44in FIG. 7E, which provides the ability to separate the opticalproperties of the modulator from the electromechanical properties of themodulator, such as addressing and the movements that result from thataddressing. This separable modulator architecture allows the structuraldesign and materials used for the electromechanical aspects and theoptical aspects of the modulator to be selected and to functionindependently of each other. Moreover, the embodiments shown in FIGS.7C-7E have additional benefits deriving from the decoupling of theoptical properties of the reflective layer 14 from its mechanicalproperties, which are carried out by the deformable layer 34. Thisallows the structural design and materials used for the reflective layer14 to be optimized with respect to the optical properties, and thestructural design and materials used for the deformable layer 34 to beoptimized with respect to desired mechanical properties.

As discussed, embodiments described herein may be used in ornamental andarchitectural devices and applications, such as for decorative glass.For example, in an architectural setting, a coated glass panel mayprovide an attractive decorative effect such that the glass appears tobe one color from one side and a different color from the other side.Moreover, when a light source positioned on one side of the panel isturned on, the panel may appear to be another color. Certain otherembodiments are used for display devices.

FIG. 8 schematically illustrates an example device 100 in accordancewith certain embodiments described herein. The device 100 comprises asubstrate 110, a first layer 120, a second layer 130, and a light source140. The substrate 110 is at least partially optically transparent. Thefirst layer 120 is positioned over the substrate 110, and the firstlayer 120 is partially optically absorptive, partially opticallyreflective, and partially optically transmissive. The second layer 130is positioned over the substrate 110 and is spaced from the first layer120 with the first layer 120 located between the substrate 110 and thesecond layer 130. The second layer 130 is partially opticallyabsorptive, partially optically reflective, and partially opticallytransmissive. In certain embodiments, the light source 140 is responsiveto a signal and positioned relative to the substrate 110 such that thefirst layer 120 and the second layer 130 are located between thesubstrate 110 and the light source 140.

In certain embodiments, light emitted from the device 100 in a firstdirection 313 toward a viewer comprises a first portion 300 of light, asecond portion 301 of light, and a third portion 302 of light. The firstportion 300 of light is incident on the substrate 110, transmittedthrough the substrate 110, transmitted through the first layer 120,reflected by the second layer 130, transmitted through the first layer120, transmitted through the substrate 110, and emitted from thesubstrate 110 in the first direction 313. The second portion 301 oflight is incident on the substrate 110, transmitted through thesubstrate 110, reflected by the first layer 120, transmitted through thesubstrate 110, and emitted from the substrate 110 in the first direction313. The third portion 302 of light is from the light source 140 and isincident on the second layer 130, transmitted through the second layer130, transmitted through the first layer 120, transmitted through thesubstrate 110, and emitted from the substrate 110 in the first direction313. In certain embodiments, at least the first portion 300 and thesecond portion 301 combine interferometrically to form the light emittedfrom the device 100 in the first direction 313. Similarly, in certainembodiments, the third portion 302 of light comprisesinterferometrically combined portions of light transmitted or reflectedfrom the various layers of the device 100. Not included in thisdescription is any stray light reflected from the surface of thesubstrate 110. Such stray light may be reduced by anti-reflectioncoatings which can be included on the substrate 110 in certainembodiments.

In certain embodiments, the substrate 110 comprises a glass or plasticmaterial. In certain embodiments, the first layer 120 and the secondlayer 130 may comprise various materials with a positive extinctioncoefficient such as aluminum, chromium, molybdenum, titanium, carbon,silver, gold, and other such materials. In certain embodiments, forexample, the first layer 120 comprises chromium. In certain embodiments,the second layer 130 comprises a metal layer (e.g., aluminum layerhaving a thickness of less than 300 Angstroms). In one embodiment, thesecond layer 130 comprises a metal having a thickness in the range of 30to 300 Angstroms. In certain embodiments, the first layer has athickness in the range of about 50 to 300 Angstroms. In one embodiment,for example, the first layer comprises chromium and the second layercomprises aluminum. The transmissivity of the second layer 130 incertain embodiments is dependent on the thickness of the second layer130.

In certain embodiments, the first layer 120 is substantially opticallyabsorptive. In other embodiments, the first layer 120 is substantiallyoptically reflective. In yet other embodiments, the first layer 120 issubstantially optically transmissive. In certain embodiments, the secondlayer 130 is substantially optically absorptive. In other embodiments,the second layer 130 is substantially optically reflective. In yet otherembodiments, the second layer 130 is substantially opticallytransmissive. In one embodiment, for example, substrate 110 comprisesglass of approximately 10 mm thickness with a refractive index ofapproximately 1.52, the layer 120 comprises Chromium of 70 Angstromsthickness, and the layer 130 comprises Aluminum of 100 Angstromsthickness. In the example embodiment, the layer 120 and the layer 130are spaced by spacing dielectric layer 150 comprising Silicon Dioxide of3400 Angstroms thickness to create an interferometric cavity capable ofmodifying the properties of light reflecting from or transmitted throughthe device by the process of optical interference (FIG. 9A). Whenilluminated from direction 300 the device of the example embodiment, thedevice 100 primarily reflects green light in the visible spectrum indirection 313 with a peak reflectivity of approximately 72% at awavelength of approximately 530 nm measured normal to the device (FIG.9B). This corresponds to a color point of x=0.26, y=0.47 in the standardCIE xyY color space as shown by the CIE Chromaticity diagram of FIG. 9C.When illuminated from direction 300 the example device transmits lightin direction 314 having a transmission spectrum also peaking at awavelength of approximately 530 nm, corresponding to a green color inthe visible spectrum (FIG. 9D). In this embodiment, if the thickness oflayer 130 is altered, the reflectivity and transmission may be altered.For example if the thickness of layer 130 is reduced to from 100Angstroms to 70 Angstroms, peak reflectivity will be reduced toapproximately 62%, while the peak reflectivity wavelength will beunchanged at approximately 530 nm, corresponding to a color point ofx=0.28, y=0.47 in the standard CIE xyY color space when viewed normal tothe device in direction 313 (FIGS. 9E-9F). In FIGS. 9E-9F, the labels“100A” and “70A” refer to the plots characterizing the embodimentsdescribed above having a layer 130 with a thickness of 100 Angstroms and70 Angstroms, respectively. In another embodiment, substrate 110comprises glass of approximately 10 mm thickness with a refractive indexof approximately 1.52, layer 120 comprises Chromium of 20 Angstromsthickness, and layer 130 comprises Aluminum of 100 Angstroms thickness.The peak reflectivity of the device of this embodiment is approximately71%, and peak reflectivity wavelength is approximately 530 nm in thevisible spectrum, normal to the device, corresponding to a color pointof x=0.29, y=0.40 in the standard CIE xyY color space (FIGS. 9G-9H). Inthis embodiment, layer 120 is primarily responsible for the saturationof the color reflected in direction 313, as shown by comparison to theembodiment described in which substrate 110 comprises glass ofapproximately 10 mm thickness, layer 120 comprises Chromium of 70Angstroms thickness and layer 130 comprises Aluminum of 100 Angstromsthickness. In FIGS. 9G-9H, the labels “70A” and “20A” refer to the plotscharacterizing the embodiments described above having a layer 120 with athickness of 70 Angstroms and 20 Angstroms, respectively. Theembodiments described above will also exhibit angular color shift. Asused herein, the term “color shift” refers to the change of coloremitted from a side of the device 100 as a function of angle from adirection perpendicular to the first layer 120 and the second layer 130.For example, the color of light emitted from the device 100 and receivedby a viewer can be dependent on the angular position of the viewerrelative to the device 100.

In certain embodiments, the first portion 300 of light incident on thesubstrate 110 and the second portion 301 of light incident on thesubstrate 110 are infrared, visible, and/or ultraviolet light. Incertain embodiments, the third portion 302 of light from the lightsource 140 is infrared, visible, and/or ultraviolet light. In oneembodiment, substrate 110 comprises glass of approximately 10 mmthickness with a refractive index of approximately 1.52. In thisembodiment, the layer 120 comprises Chromium of 70 Angstroms thickness,the layer 130 comprises Aluminum of 100 Angstroms thickness, and thelayer 120 and the layer 130 are spaced by spacing dielectric layer 150comprising Silicon Dioxide of 5000 Angstroms thickness, to create aninterferometric cavity. When illuminated from direction 300 the deviceof the example embodiment primarily reflects light in both the infra redspectrum and the visible spectrum in direction 313 with a peakreflectivity of approximately 68% at wavelengths of approximately 755 nmand 72% at a wavelength of 510 nm measured normal to the device (FIG.10).

In certain embodiments, the light source 140 comprises a backlight, asschematically illustrated by FIG. 8. The backlight of certain suchembodiments comprises a light guide slab that receives light from alight generator (e.g., an LED, where light from the LED is injectedalong an edge of the light guide slab), guides the light along the lightguide slab, and redirects and emits the light towards the device therebyproviding illumination that may be substantially uniform or non-uniformto take advantage of device transmission and reflection properties tocreate patterns, graphics, or images with luminance or chromaticcontrast when viewed from direction 313 or 314. The light guide slab caninclude extractor features located on a rear or front surface (withrespect to the second layer 130) of the light guide slab which disruptthe propagation of light within the light guide slab and cause the lightto be uniformly emitted across a front surface of the light guide slabtowards a front surface of the device 100. In certain embodiments, thelight source 140 comprises a fluorescent light generator. In otherembodiments, the light source 140 comprises an incandescent lightgenerator, an LED, or another type of light generator. In certain otherembodiments, the light source 140 can comprise a substantiallyreflective surface which reflects or emits a substantial portion of thelight which reaches the light source 140 after being transmitted throughthe substrate 110, the first layer 120, and the second layer 130. Incertain embodiments, there may be a separation between the light source140 and the other portions of the device 100. In certain suchembodiments, for example, there may be a physical separation between thelight source 140 and the layer 130. Additionally, in some embodiments,the light incident upon and modulated by the device 100 includes ambientor natural light, such as light from the sun, for example.

In certain embodiments, the light source 140 is responsive to the signal(e.g., from a controller) by changing between multiple states. Forexample, in certain embodiments, in response to the signal, the lightsource 140 can turn “on” and “off”. In other embodiments, the lightsource 140 may be responsive to the signal by changing to emit lighthaving different properties, such as, for example, light havingdifferent brightness levels or different colors. In one embodiment, thelight source 140 is responsive to the signal by changing from emittinglight having a first selected brightness to emitting light having asecond selected brightness different from the first selected brightness.In certain embodiments, the light source 140 is responsive to the signalby changing from emitting light having a first selected color toemitting light having a second selected color different from the firstselected color. In certain embodiments, the light source 140 isresponsive to the signal by changing from emitting light of a firstselected color, thereby modulating angular color shift and intensityover a predetermined range of angles (e.g., 0 to 30 degrees) from adirection perpendicular to the first layer 120 and the second layer 130to emitting light exhibiting a second selected color, thereby modulatingangular color shift and intensity over a predetermined range of angles(e.g., 0 to 30 degrees) from a direction perpendicular to the firstlayer 120 and the second layer 130 where the second selected color shiftis different from the first selected angular color shift and intensity.By modulating the signal in certain embodiments, one or more propertiesof the light emitted in the first direction 313 can be modulated.

Light resulting from the interference of light reflected from aplurality of layers can be referred to as “interferometricallyreflected” light. In certain embodiments, the first portion 300 of lightand the second portion 301 of light interfere with one another toproduce interferometrically reflected light which comprises asubstantial portion of the light reflected from the device 100. Incertain other embodiments, the reflected light emitted from the device100 can comprise light from other reflections from other interfaces(e.g., the air-substrate interface), light reflected from other layers,and light from multiple reflections between these interfaces (e.g.,light reflected multiple times between the first layer 120 and thesecond layer 130).

In certain embodiments, the first portion 300 of light and the secondportion 301 of light interfere to produce light having a first color,and the third portion 302 of light has a second color different from thefirst color. In certain embodiments, the first portion 300 of light andthe second portion 301 of light interfere to produce light having afirst color, and the light emitted from the device 100 in the firstdirection 313 (e.g., the combination of the interferometricallyreflected light and the third portion 302 of light) has a second colordifferent from the first color.

In certain embodiments, the light emitted from the device 100 in thefirst direction 313 has a first color when the light source 140 emitslight. The first color of such embodiments results from the combinationof the interferometrically reflected light and the third portion 302 oflight. In certain embodiments, the light emitted by the device 100 inthe first direction 313 has a second color, which can be different fromthe first color, when the light source 140 does not emit light. Thesecond color of such embodiments results from the interferometricallyreflected light without the third portion 302 of light.

In certain embodiments, the light emitted by the device 100 in the firstdirection 313 has a first color when the light source 140 emits lightand ambient light is incident on the device 100 (e.g., incident on thesubstrate 110). The first color of such embodiments results from thecombination of the interferometrically reflected light and the thirdportion 302 of light. In certain embodiments, the light emitted by thedevice 100 in the first direction 313 has a second color, which can bedifferent from the first color, when the light source 140 emits lightand ambient light is not incident on the device 100. The second color ofsuch embodiments results from the third portion 302 of light without theinterferometrically reflected light. In certain embodiments, the lightemitted by the device 100 in the first direction 313 has a third color,which can be different from either the first color or the second color,when the light source 140 does not emit light and ambient light isincident on the device 100. The third color of such embodiments resultsfrom the interferometrically reflected light without the third portion302 of light. In one embodiment, substrate 110 comprises glass ofapproximately 10 mm thickness, layer 120 comprises Aluminum of 40Angstroms thickness, layer 130 comprises Aluminum also of 40 Angstromsthickness, and layer 120 and 130 are spaced by spacing dielectric layer150 comprising Silicon Dioxide of 3200 Angstroms thickness to create aninterferometric cavity. When illuminated from direction 300 the devicewill reflect blue light in direction 313, normal to the device, with apeak wavelength of 470 nm and peak reflectivity of approximately 56%(not including losses through substrate materials or due to reflectionat material/air interfaces). The example interferometric devicedescribed is semi-transparent and will transmit light in direction 302when illuminated by light source 140. This embodiment will transmitgreen light with a peak wavelength of 540 nm and a transmission ofapproximately 45% (not including losses through substrate materials, ordue to reflection at material/air interfaces), as shown by the plot ofFIG. 11A and the CIE chromaticity diagram of FIG. 11B. The light emittedin direction 313 will comprise a combination of the interferometricallyreflected light and light 302, which will vary in perceived coloraccording to the intensity of the light source 140 and the intensity ofthe light incident on the device.

In certain embodiments, the first portion 300 of light and the secondportion 301 of light interfere to produce light having a first color andwhich exhibits a first angular color shift, and the third portion 302 oflight has a second color and exhibits a second angular color shiftdifferent from the first angular color shift. In certain embodiments,the first portion 300 of light and the second portion 301 of lightinterfere to produce light having a first color which exhibits a firstangular color shift, and the light emitted from the device 100 in thefirst direction 313 (e.g., the combination of the interferometricallyreflected light and the third portion 302 of light) has a second colorand exhibits a second angular color shift different from the firstangular color shift. In one embodiment, substrate 110 comprises glass ofapproximately 10 mm thickness, layer 120 comprises Aluminum of 40Angstroms thickness, layer 130 comprises Aluminum also of 40 Angstromsthickness, and layer 120 and layer 130 are spaced by spacing dielectriclayer 150 comprising Silicon Dioxide of 3200 Angstroms thickness tocreate an interferometric cavity. When illuminated from direction 300the device will reflect blue light in direction 313, normal to thedevice, with a peak wavelength of 470 nm and peak reflectivity ofapproximately 56% (not including losses through substrate materials, ordue to reflection at material/air interfaces). The interferometricdevice of the example embodiment is semi-transparent and will transmitlight in direction 302 when illuminated by light source 140. Thisembodiment will transmit green light with a peak wavelength of 540 nmand a transmission of approximately 45% (not including losses throughsubstrate materials, or due to reflection at material/air interfaces),as shown by FIG. 11A. FIG. 11B shows the same as a CIE chromaticitydiagram. FIGS. 12A and 12B show how the reflected and transmitted colorvaries with view angle. FIG. 12B assumes that the viewer is within thesubstrate 110 and does not account for the substrate to air interface. Arefractive index change at that interface will alter the perceived colorshift. As a result, if the viewer is in air (N=1) and the substrate isglass (N=1.52), then the viewer will see a reduced amount of color shiftfor a given view angle with respect to the substrate.

In certain embodiments, the light emitted from the device 100 in thefirst direction 313 has a first color and exhibits a first angular colorshift when the light source 140 emits light. The first angular colorshift of such embodiments results from the combination of theinterferometrically reflected light and the third portion 302 of light.In certain embodiments, the light emitted by the device 100 in the firstdirection 313 has a second color and exhibits a second angular colorshift, which can be different from the first angular color shift, whenthe light source 140 does not emit light. The second angular color shiftof such embodiments results from the interferometrically reflected lightwithout the third portion 302 of light.

In certain embodiments, the light emitted by the device 100 in the firstdirection 313 has a first color and exhibits a first angular color shiftwhen the light source 140 emits light and ambient light is incident onthe device 100 (e.g., incident on the substrate 110). The first angularcolor shift of such embodiments results from the combination of theinterferometrically reflected light and the third portion 302 of light.In certain embodiments, the light emitted by the device 100 in the firstdirection 313 has a second color and exhibits a second angular colorshift, which can be different from the first angular color shift, whenthe light source 140 emits light and ambient light is not incident onthe device 100. The second angular color shift of such embodimentsresults from the third portion 302 of light without theinterferometrically reflected light. In certain embodiments, the lightemitted by the device 100 in the first direction 313 has a first colorand exhibits a third angular color shift, which can be different fromeither the first angular color shift or the second angular color shift,when the light source 140 does not emit light and ambient light isincident on the device 100. The third angular color shift of suchembodiments results from the interferometrically reflected light withoutthe third portion 302 of light. Referring again to the exampleembodiment described above with respect to FIGS. 12A-12B in which thesubstrate 110 comprises glass of approximately 10 mm thickness, layer120 comprises Aluminum of 40 Angstroms thickness, layer 130 comprisesAluminum also of 40 Angstroms thickness, and layer 120 and layer 130 arespaced by spacing dielectric layer 150 comprising Silicon Dioxide of3200 Angstroms thickness, a viewer will see 313 as the combination ofthe reflected light (300, 301) and transmitted light 302. FIG. 13 showshow the reflected and transmitted color variation with view angle (for aviewer within substrate 110, so ignoring additional reflections fromsubstrate 110.) For a viewer normal to the IMOD, depending on thebrightness of the light source 140 and the reflected portion of light,the perceived color will lie on a line from A to B as shown in FIG. 13.Similarly at an angle of 30 degrees, the color will lie on a line from Cto D. This example also shows how an illuminated semi-transparent IMODcan be used to produce color that not only varies with view angle, butwhich is not a color that can be directly created by a purely reflectiveIMOD.

In certain embodiments, the device 100 is viewable from both the firstdirection 313 and in a second direction 314 generally opposite to thefirst direction 313. For example, the device 100 of certain suchembodiments can be viewed from a first position on a first side of thedevice 100 and from a second position on a second side of the device100. In certain embodiments, the light emitted from the device 100 inthe second direction 314 comprises a fourth portion 306 of light, afifth portion 307 of light, and a sixth portion 312 of light. The fourthportion 306 of light in certain embodiments is incident on the substrate110, transmitted through the substrate 110, transmitted through thefirst layer 120, transmitted through the second layer 130, and emittedfrom the device 100 in the second direction 314. The fifth portion 307of light in certain embodiments is incident on the second layer 130,transmitted through the second layer 130, reflected from the first layer120, transmitted through the second layer 130, and emitted from thedevice 100 in the second direction 314. The sixth portion 312 of lightin certain embodiments is incident on the second layer 130, reflectedfrom the second layer 130, and emitted from the device 100 in the seconddirection 314. In certain embodiments, the fifth portion 307 of lightcomprises light emitted by the light source 140 and the sixth portion312 of light comprises light emitted by the light source 140.

In certain embodiments, the light emitted from the device 100 in thefirst direction 313 has a first color, and the light emitted from thedevice 100 in the second direction 314 has a second color. In certainsuch embodiments, the first color and the second color are substantiallythe same, while in certain other such embodiments, the first color andthe second color are different. In certain embodiments, the lightemitted from the device 100 in the first direction 313 has a first colorand exhibits a first angular color shift, and the light emitted from thedevice 100 in the second direction 314 has a second color and exhibits asecond angular color shift. In certain such embodiments, the firstangular color shift and the second angular color shift are substantiallythe same, while in certain other such embodiments, the first angularcolor shift and the second angular color shift are different. In oneembodiment, substrate 110 comprises glass of approximately 10 mmthickness, layer 120 comprises Aluminum of 40 Angstroms thickness, layer130 comprises Aluminum also of 40 Angstroms thickness, and layer 120 andlayer 130 are spaced by spacing dielectric layer 150 comprising SiliconDioxide of 3200 Angstroms thickness to create an interferometric cavity.This symmetrically designed IMOD will tend to exhibit similar reflectedcolors in direction 313 and 314 (FIGS. 14A-14B). In this exampleembodiment, layer 120 is positioned against glass and layer 130 ispositioned in air (for simplicity, and not by way of limitation, thereis no backlight 140 included in this example embodiment). The CIEChromaticity diagram of FIG. 14B shows that the reflected colors indirection 313 and 314 are similar. In practice, the difference inrefractive index between substrate 110 and the air surrounding layer 130accounts for the slight difference in symmetry. If layer 130 were alsopositioned against glass, the device reflection would be symmetric. Forsimplicity, the viewer is assumed to be normal to the device and on side313 the viewer is assumed to be within substrate 110, so that thesubstrate 110 to air interface is not included. The transmitted color issubstantially the same for ray 306 and 302 in the example embodiment. Inanother embodiment, the substrate 110 comprises glass of approximately10 mm thickness with a refractive index of approximately 1.52. Layer 120comprises Chromium of 70 Angstroms thickness, layer 130 comprisesAluminum of 100 Angstroms thickness, and layer 120 and layer 130 arespaced by spacing dielectric layer 150 comprising Silicon Dioxide of3400 Angstroms thickness. In this example, the layer 120 is positionedagainst glass and the layer 130 is positioned in air (for simplicity,and not by way of limitation, no backlight 140 is included in thisexample embodiment). The CIE Chromaticity diagram of FIG. 14C shows thatthe reflected colors in direction 313 and direction 314 are different.For simplicity, the viewer is assumed to be normal to the device and onside 313 the viewer is assumed to be within substrate 110, so thesubstrate 110 to air interface is not included. The transmitted color issubstantially the same for ray 306 and 302 in the example embodiment.

In certain embodiments, the device 100 comprises a region 150 locatedbetween the first layer 120 and the second layer 130. The region 150 ofcertain embodiments comprises a dielectric layer and is at leastpartially optically transparent. In certain embodiments, at least aportion of the region 150 is filled with air. In certain suchembodiments, at least one of the first layer 120 and the second layer130 is selectively movable so as to change a spacing between the firstlayer 120 and the second layer 130. Thus, in certain embodiments, thefirst layer 120 and the second layer 130 form an actuableinterferometric modulator as described herein. In certain embodiments,the device 100 is an actuatable element (e.g., a pixel or sub-pixel) ofa display system. By selectively moving at least one of the first layer120 and the second layer 130 so as to change a spacing between the firstlayer 120 and the second layer 130, in certain embodiments, one or moreproperties of the light emitted in the first direction 313 can bemodulated.

In certain embodiments, the at least one of the first layer 120 and thesecond layer 130 which is selectively movable comprises a supportstructure which mechanically strengthens the layer. In some embodiments,the support structure comprises a transparent material. In otherembodiments, the support structure comprises a non-transparent material(e.g., a metal ring) which is positioned so as to not affect the opticalproperties of the device.

FIG. 15 schematically illustrates an example device 100 comprising afluorescent material 160 in accordance with certain embodimentsdescribed herein. The device 100 comprises a substrate 110, a firstlayer 120, and a second layer 130. The substrate is at least partiallyoptically transparent. The first layer 120 is positioned over thesubstrate 110, and the first layer 120 is partially opticallyabsorptive, partially optically reflective, and partially opticallytransmissive. The second layer 130 is positioned over the substrate 110and is spaced from the first layer 120 with the first layer 120 locatedbetween the substrate 110 and the second layer 130. The second layer 130is partially optically absorptive, partially optically reflective, andpartially optically transmissive. The fluorescent material 160 ispositioned relative to the substrate 110 such that the first layer 120and at least a portion of the second layer 130 are located between thesubstrate 110 and the fluorescent material 160. In certain embodiments,the fluorescent material 160 is responsive to ultraviolet light incidenton the substrate 110, transmitted through the substrate 110, transmittedthrough the first layer 130, and transmitted through the at least aportion of the second layer 130 by generating visible light. At least aportion of the visible light from the fluorescent material 160 incertain embodiments is transmitted through the second layer 130, thefirst layer 120, and the substrate 110 to contribute to the lightemitted in the first direction 313. In certain such embodiments, thefluorescent material 160 serves as the light source 140.

FIG. 16 schematically illustrates an example device 100 comprising athird layer 170 in accordance with certain embodiments described herein.In certain embodiments, the third layer 170 may comprise variousmaterials such as aluminum, chromium, molybdenum, titanium, carbon,silver, gold, and other materials. The third layer 170 is over thesubstrate 110 and spaced from the first layer 120 and from the secondlayer 130. The third layer 170 is partially optically absorptive,partially optically reflective, and partially optically transmissive. Incertain embodiments, the third layer 170 has a thickness in a range frombetween 20 and 300 Angstroms thick. In certain embodiments, the thirdlayer 170 comprises chromium. In certain embodiments, the third layer170 is substantially optically absorptive. In other embodiments, thethird layer 170 is substantially optically reflective. In yet otherembodiments, the third layer 170 is substantially opticallytransmissive.

As shown schematically by FIG. 16, in certain embodiments, the thirdlayer 170 is located between the first layer 120 and the second layer130. The device 100 of certain embodiments further comprises a region150 (e.g., an at least partially optically transparent dielectric layeror a region filled with air) located between the third layer 170 and thefirst layer 120, and a region 190 (e.g., an at least partially opticallytransparent dielectric layer or a region filled with air) locatedbetween the third layer 170 and the second layer 130.

FIG. 17 schematically illustrates another example device 100 comprisinga third layer 170 in accordance with certain embodiments describedherein. The third layer 170 is positioned such that the second layer 130is located between the first layer 120 and the third layer 170. Thedevice 100 of certain embodiments further comprises a region 150 (e.g.,an at least partially optically transparent dielectric layer or a regionfilled with air) located between the first layer 120 and the secondlayer 130, and a region 190 (e.g., an at least partially opticallytransparent dielectric layer or a region filled with air) locatedbetween the second layer 130 and the third layer 170.

The combination of the layers 120, 150, 130, 170, 190 can comprise adual cavity interferometric modulator in certain embodiments. Theadditional layers 170, 190 of material as compared to FIG. 8 can provideflexibility in design such that the modulator can be designed to reflector transmit additional colors. In certain embodiments, the layers 150,190 can be described as spacer layers and layers 120, 170 can bedescribed absorber layers. In other embodiments, the layer 170 may be anabsorber layer and layers 120, 130 may act as partial reflector layers.In some embodiments, the layers 150, 190 have equal thicknesses. Inother embodiments, the layers 150, 190 have different thicknesses. Inone embodiment, substrate 110 comprises glass of approximately 10 mmthickness with a refractive index of approximately 1.52, the layers 120,170 comprise Chromium of 70 Angstroms thickness, layer 130 comprisesAluminum of 100 Angstroms thickness, and spacing dielectric layers 150,190 comprise Silicon Dioxide of 3400 Angstroms thickness (FIG. 18A).FIGS. 18B-18C show the reflected color normal to the substrate indirection 313 (assuming no backlight). Comparing this example to FIGS.9B and 9C for a viewer standing in air, and including a front surfacereflection from substrate 110, the peak wavelength is almost unchangedat 520 nm, but shows a sharper peak and correspondingly more saturatedcolor as shown by the CIE chromaticity diagram of FIG. 9C, for example.

FIG. 19 schematically illustrates an example device 100 comprising apassivation layer 200 in accordance with certain embodiments describedherein. The passivation layer 200 is positioned such that the secondlayer 130 is located between the passivation layer 200 and the substrate110. In certain embodiments, the passivation layer 200 comprises an atleast partially optically transparent dielectric material (e.g., silicondioxide) and has a thickness in a range between about 300 Angstroms andabout 4000 Angstroms. In certain embodiments, the light emitted from thedevice 100 in the first direction 313 has a color which is dependent onthe thickness of the passivation layer 200 (e.g., due to the effect ofthe passivation layer 200 on the interferometrically reflected lightand/or on the light transmitted through the device 100 in the firstdirection 313). In certain such embodiments, the thickness of thepassivation layer 200 is selected to tailor the color of the lightemitted from the device 100 in the first direction 313 to be a selectedcolor. For example, the passivation layer 200 can be configured to havea selected thickness within the range described to provide both thedesired passivation and the desired tailoring of the color emitted fromthe device 100 in the first direction 313.

In certain embodiments, the light emitted from the device 100 in thefirst direction 313 is dependent on an index of refraction of thepassivation layer 200. In some embodiments, the index of refraction ofthe passivation layer 200 is substantially different from the index ofrefraction of the surrounding medium. In certain embodiments, thepassivation layer 200 comprises silicon dioxide. In other embodiments,the passivation layer 200 comprises another type of oxide or a polymer.

In certain embodiments, an additional layer is in contact with thepassivation layer 200 such that the passivation layer 200 is positionedbetween the region 150 and the additional layer. In some embodiments,the color of the light emitted from the device in the first direction313 and 314 can be tailored by the index of refraction of the additionallayer. In certain embodiments, the additional layer comprises anadhesive material such as glue or tape. In some embodiments, theadditional layer comprises ink. In one embodiment, for example, as shownby FIG. 20A, the substrate 110 comprises glass of approximately 10 mmthickness with a refractive index of approximately 1.52. An IMOD isconstructed on the substrate so that layer 120 comprises Chromium of 70Angstroms thickness, the layer 130 comprises Aluminum of 60 Angstromsthickness, and the layer 120 and the layer 130 are spaced by spacingdielectric layer 150 comprising Silicon Dioxide of 2700 Angstromsthickness. In the example embodiment, layer 200 comprises SiliconDioxide. The layer 200 side of the IMOD is bonded to pieces of PET withan adhesive index matched to the PET, with a refractive index of 1.61,so that some areas of the IMOD are bonded and some are not. When viewedfrom direction 314 and direction 313, the reflected and transmittedcolor will vary, both between areas bonded with PSA, and those in air,and if the thickness of layer 200 is varied. FIG. 20B shows this effectfor embodiments where the air is adjacent to the layer 200 and where thelayer 200 is varied from 1200 Angstroms to 2700 Angstroms (labels A andD). FIG. 20B also shows this effect for an embodiment where the layer200 is bonded to material having a refractive index of 1.61 and wherethe layer 200 is varied from 1200 Angstroms to 2700 Angstroms (labels Band C). FIG. 20B assumes that the viewer is normal to the device 100. Inthe example embodiment, and as shown by FIG. 20B, the “color tuning”effect seen from direction 314 is relatively large. A “color tuning”effect is also seen from direction 313 and in the transmitted color. Asshown, there is a narrower range of variation of color with variation ofthe layer 200 from 1200 Angstroms to 2700 Angstroms with the layer 200adjacent to the PSA. The portion of FIG. 20B identified by the label“Reflection 313” represents the total range of variation of color fromdirection 313 with variation of the layer 200 from 1200 Angstroms to2700 Angstroms and for a change from air to a PSA interface.

FIG. 21 schematically illustrates an example device 100 comprising afirst glass layer 210 and a second glass layer 220 in accordance withcertain embodiments described herein. The structure 270 comprises thesubstrate 110, the first layer 120, and the second layer 130 and spacerlayer 150. The structure 270 comprising the substrate 110, the firstlayer 120, and the second layer 130 and spacer layer 150 is laminatedand located between the first glass layer 210 and the second glass layer220. In certain embodiments, one or more adhesive layers 230 are used tolaminate the structure comprising the substrate 110, the first layer120, and the second layer 130 with the first glass layer 210 and thesecond glass layer 220. In certain embodiments, at least one of thefirst glass layer 210 and the second glass layer 220 comprises texturedglass. The substrate 110, the first layer 120, the second layer 130, andthe spacer layer 150 comprise an IMOD, which may be designed to exhibitspecific colors in directions 313, 314 and 302, 306. As aninterferometric device it can exhibit on axis colors that color shift asthe viewer changes angle relative to the structure. A textured laminatecan be designed with either specific or random angular features on thesurface so that light emerging toward a viewer through planar areas ofthe substrate will emerge at a different angle relative to the IMODcompared to light emerging through a textured feature. Therefore theviewer will see different colors across the textured surface. Examplesof textured laminates can be found in U.S. patent application Ser. No.12/220,947, titled “DEVICES AND METHODS FOR ENHANCING COLOR SHIFT OFINTERFEROMETRIC MODULATORS”, filed Jul. 29, 2008, which is incorporatedin its entirety by reference herein.

FIG. 22 schematically illustrates an example device 100 having a firstlayer 120, a second layer 130, a third layer 240, and a fourth layer 250in accordance with certain embodiments described herein. The first layer120 and the second layer 130 are over a first surface of the substrate110. The third layer 240 and the fourth layer 250 are over a secondsurface of the substrate 110. The third layer 240 is partially opticallyabsorptive, partially optically transmissive, and partially opticallyreflective. The fourth layer 250 is spaced from the third layer 240,with the third layer 240 located between the substrate 110 and thefourth layer 250. The fourth layer 250 is partially opticallyabsorptive, partially optically transmissive, and partially opticallyreflective. In certain embodiments, the device 100 further comprises alight source 140 positioned relative to the substrate 110 such that thefirst layer 120 and the second layer 130 are located between thesubstrate 110 and the light source 140.

As schematically illustrated by FIG. 22, in certain embodiments, thedevice 100 further comprises a spacer 260 (e.g., an at least partiallyoptically transparent dielectric layer or a region filled with air)located between the third layer 240 and the fourth layer 250. In certainembodiments, one or both of the spacer 150 located between the firstlayer 120 and the second layer 130 and the spacer 260 located betweenthe third layer 240 and the fourth layer 250 comprises a region filledwith air. The structure comprising layers 120, 150, 130 and thestructure comprising layers 260, 250, 240 may each be described asindividual IMODs in certain embodiments. The structure comprising layers120, 150, 130 will be described herein as IMOD I and the structurecomprising layers 260, 250, 240 will be described herein as IMOD II.These descriptions are for the purposes of illustration and are notlimiting. In one embodiment, for example, substrate 110 comprises ofglass of approximately 10 mm thickness with a refractive index ofapproximately 1.52, the layer 120 comprises Chromium of 70 Angstromsthickness, the layer 130 comprises Aluminum of 40 to 100 Angstromsthickness, and the layer 120 and the layer 130 are spaced by spacingdielectric layer 150 comprising Silicon Dioxide of 1000 to 5000Angstroms thickness. As has been described herein, the spacer 150 can beselected to provide a specific transmitted and reflected color, with thelayer 120 (e.g., absorber layer) and the layer 130 (e.g., reflectorlayer) selected to provide the desired brightness and color saturation.Layers 250, 240 and spacer 260 may be selected in a similar way. Each ofIMODs I and II are independent but, depending on the level oftransmission, the IMODs can interact so the viewer will see colors thatare a combination of the two. In one embodiment, for example, layer 120comprises Chromium of 70 Angstroms thickness, the layer 130 comprisesAluminum of 60 Angstroms thickness, and the layer 120 and the layer 130are spaced by spacing dielectric layer 150 comprising Silicon Dioxide of2000 Angstroms thickness. In the example embodiment, the layer 240comprises Chromium of 70 Angstroms thickness, the layer 250 comprisesAluminum of 60 Angstroms thickness, and the layer 240 and the layer 250are spaced by spacing dielectric layer 260 comprising Silicon Dioxide of4250 Angstroms thickness. The resulting on axis transmission plots forIMODs I and II are shown in FIG. 23 (front reflections are excluded inFIG. 23). IMOD I has a first order red transmission response, IMOD II ismagenta, but the effect of overlaying them as described will be for IMODII to act as a filter for the red IMOD I, increasing its colorsaturation.

In certain embodiments, a plurality of devices, including one or moredevices 100, can be arranged in a manner generally similar to theembodiments described above with respect to, for example, FIGS. 1-5. Incertain embodiments, the plurality of devices can have differentinterferometric and/or transmissive performance. For example, aplurality of devices can be arranged in a row/column array. Contrastamong these different devices can be used to generate a viewable image.For example, in certain embodiments, multiple devices can be formed froma patterned layered structure over the substrate 110. A first device100, for example, can comprise a first layer 120 and a second layer 130as described herein, and can be the source of both interferometricallyreflected light and light transmitted through the first device 100. Asecond device can comprise a first layer that is partially opticallyabsorptive, partially optically transmissive, and partially opticallyreflective (e.g., a chromium layer) and a second layer spaced from thefirst layer such that the second layer is located between the substrate110 and the first layer. The second layer can be at least partiallyoptically reflective and substantially optically non-transmissive. Incertain such embodiments, the first layer and the second layer areportions of an interferometric modulator as described herein.

In certain embodiments, the first device 100 exhibits a first colorwhich is the result of a first portion 300 of light, a second portion301 of light, and a third portion 302 of light being emitted in a firstdirection 313 from the device 100 as described herein. In certainembodiments, the first portion 300 of light and the second portion 301of light interfere to produce light having a first color, and the thirdportion 302 of light has a second color different from the first color.

In certain embodiments, the second device exhibits a second color whichis the result of a fourth portion of light incident on the substrate110, transmitted through the substrate 110, transmitted through thefirst layer of the second device, reflected by the second layer of thesecond device, transmitted through the first layer of the second device,transmitted through the substrate 110, and emitted from the device inthe first direction 313, and a fifth portion of light incident on thesubstrate 110, transmitted through the substrate 110, reflected by thefirst layer of the second device, transmitted through the substrate 110,and emitted from the second device in the first direction 313. Thefourth portion of light and the fifth portion of light interfere toproduce light having the second color. In certain embodiments, thesecond color is different from the first color.

In certain embodiments, the plurality of devices further comprises ananti-reflection coating on a surface of the substrate 110 such that thesubstrate 110 is located between the anti-reflective coating and thefirst layer 120 of the first device 100 and the first layer of thesecond device. In certain embodiments, the first layer 120 of the firstdevice 100 is contiguous with the first layer of the second device(e.g., the first layer 120 of the first device 100 and the first layerof the second device can be portions of a common layer). For example, anChromium layer can have one or more portions that have a thickness lessthan 1000 Angstroms serving as the first layer 120 of the first device100, and also serving as the first layer of the second device.

In certain embodiments, the plurality of devices further comprises athird device which is substantially transmissive to light incident onthe third device. In certain such embodiments, the first device 100exhibits a first color, the second device exhibits a second colordifferent from the first color, and the third device exhibits a thirdcolor different from both the first color and the second color. Contrastamong the first, second, and third devices can be used to generate aviewable image.

The effect of varying reflector and absorber thickness will now beillustrated with reference to certain embodiments of the device 100 ofFIG. 24A wherein substrate 110 comprises glass of approximately 10 mmthickness with a refractive index of approximately 1.52, the layer 120comprises Chromium of 20 to 80 Angstroms thickness, the layer 130comprises Aluminum of 30 to 150 Angstroms, and the layer 120 and thelayer 130 are spaced by spacing dielectric layer 150 comprising SiliconDioxide of 90 to 450 Angstroms thickness. For simplicity, the view is onaxis from within substrate 110 (e.g., ignoring the substrate to airinterface). FIGS. 24B-24D illustrate the reflectivity, a CIEchromaticity diagram, and the transmittance, respectively, of exampleembodiments of the device 100 of FIG. 24A wherein the layer 120comprises Chromium of 70 Angstroms thickness, the spacer layer 150comprises Silicon Dioxide of 3400 Angstroms thickness, and the reflectorlayer 130 comprises Aluminum and is varied from between 30 and 150Angstroms thickness. As illustrated by FIGS. 24B-24D, the effect isrelatively larger on the reflectivity and transmittance and there isrelatively less effect on the color saturation. FIGS. 24E-24F show thereflectivity/transmittance and a CIE chromaticity diagram, respectively,of embodiments of the device 100 of FIG. 24A where the reflector layer130 comprises Aluminum 60 Angstroms thick, the spacer layer 150comprises Silicon Dioxide 3400 Angstroms thick, and the absorber layer120 comprises Chromium and is varied from 20 Angstroms to 70 Angstromsthickness. The effect on the color is different than the embodimentillustrated with respect to FIGS. 24B-24D and there is a relativelygreater impact on color saturation.

One aspect of an IMOD device is angular color shift. FIG. 25A shows aCIE chromaticity diagram of another embodiment of a device 100 (onglass) where the absorber layer 120 comprises Chromium 70 Angstromsthick, the spacer layer 150 comprises Silicon Dioxide 3400 Angstromsthick, and the reflector layer 130 comprises Aluminum 60 Angstromsthick. The example embodiment exhibits a second order color with peakreflectivity of 535 nm on axis in direction 313. View angle (from withinsubstrate 110, for simplicity and not by way of limitation) is variedfrom 0 to 30 degrees in the example embodiment.

FIG. 25B shows a CIE chromaticity diagram of another example embodimentwherein the absorber layer 120 and the reflector layer 130 comprise thesame materials having the same thicknesses as the embodiment describedwith respect to FIG. 25A but where the spacer layer 150 is 1580Angstroms thick. The embodiment illustrated with respect to FIG. 25B hasa green reflection peaking at 535 nm, similar to the embodimentillustrated with respect to FIG. 25A, but as a first order colorresponse, it exhibits less angular color shift. FIGS. 25C-25D illustrateexample embodiments of the device 100 wherein the absorber layer 120 andthe reflector layer 130 comprise the same materials having the samethicknesses as the embodiments described with respect to FIGS. 25A-B,but where the spacer layer 150 comprises Zinc Oxide (which has higherrefractive index than Silicon Dioxide) and air (lower index),respectively. The spacer thickness for the embodiments of FIGS. 25C-25Dis adjusted in each case to provide the same peak reflected wavelength(535 nm) on axis. Each figure shows the effect (viewed from withinsubstrate 110 for simplicity, and not by way of limitation) of varyingthe view angle from 0 to 30 degrees. As illustrated, the embodimentshaving lower index spacers exhibit more color shift. For example, thehigher index spacer layer 150 (e.g., Zinc Oxide) of FIG. 25C has thesame peak reflectivity of 535 nm at 0 degrees viewing angle, butexhibits less color shift than the lower index spacer layer 150 (e.g.,Silicon Dioxide) of the embodiment of FIG. 25B. This provides anotherdesign parameter for a semi transparent IMOD. In certain embodiments,the IMOD may also be combined with texture to accentuate the color shifteffect, or diffusive materials which can be used to de-emphasize thecolor shift effect, depending on the aesthetic desired.

FIG. 26 illustrates another embodiment of the device 100 wherein theabsorber layer 120 and the reflector layer 130 comprise the samematerials having the same thicknesses as the embodiments described withrespect to FIGS. 24A-24D, viewed on axis, but wherein the spacer layer150 is varied from 1000 Angstroms to 4250 Angstroms, through first andsecond order colors. FIG. 26 shows that as the spacer thickness variesthe color will vary over a relatively wide range, and identifies colorsthat are first order (less saturated) or second order (more saturated).Colors at the extreme end of the range depicted (for example themagentas with spacer layers 150 approximately 4000 Angstroms or more)may also include third order colors, in addition to second order colors.

Although certain embodiments and examples are discussed above, it isunderstood that the inventive subject matter extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the embodiments and obvious modifications and equivalentsthereof. Thus, for example, in any method or process disclosed herein,the acts or operations making up the method/process may be performed inany suitable sequence and are not necessarily limited to any particulardisclosed sequence. Various aspects and advantages of the embodimentshave been described where appropriate. It is to be understood that notnecessarily all such aspects or advantages may be achieved in accordancewith any particular embodiment. Thus, for example, it should berecognized that the various embodiments may be carried out in a mannerthat achieves or optimizes one advantage or group of advantages astaught herein without necessarily achieving other aspects or advantagesas may be taught or suggested herein.

1. A device comprising: a substrate that is at least partially opticallytransparent; a first layer that is partially optically absorptive,partially optically reflective, and partially optically transmissive,the first layer being configured to reflect in a first direction a firstportion of light that is incident on the substrate and transmittedthrough the substrate to the first layer; a second layer disposed suchthat the first layer is between the substrate and the second layer, thesecond layer being partially optically absorptive, partially opticallyreflective, and partially optically transmissive, the second layerconfigured to reflect in the first direction a second portion of lightthat is incident on the substrate and passes through the substrate andthe first layer to the second layer; and a light source configured toemit a third portion of light, the light source disposed to emit thethird portion of light through the substrate in the first direction anddisposed such that the second layer is between the light source and thefirst layer; wherein a light emitted from the device in the firstdirection is of a first color when the light source emits the thirdportion of light and is of a second color when the light source does notemit the third portion of light, the second color being different fromthe first color.
 2. The device of claim 1, wherein the second layer hasa thickness in the range of 30 to 300 Angstroms.
 3. The device of claim2, wherein the second layer comprises aluminum and has a thickness lessthan 300 Angstroms
 4. The device of claim 1, wherein at least one of thefirst layer and the second layer is selectively movable so as to changea spacing between the first layer and the second layer.
 5. The device ofclaim 1, wherein the first portion of light and the second portion oflight interfere to produce light of a color that is different than acolor of the third portion of light.
 6. The device of claim 1, whereinthe light source is responsive to a signal by changing from emittinglight of a first selected color to emitting light of a second selectedcolor that is different than the first selected color.
 7. The device ofclaim 1, wherein the first layer is configured to reflect in a seconddirection a fourth portion of light that is incident on the second layerand transmitted through the second layer to the first layer.
 8. Thedevice of claim 7, wherein the second layer is configured to reflect inthe second direction a fifth portion of light that is incident on thesecond layer.
 9. The device of claim 8, wherein the second direction isgenerally opposite to the first direction.
 10. The device of claim 9,wherein the fourth portion of light comprises light emitted by the lightsource.
 11. The device of claim 10, wherein the fifth portion of lightcomprises light emitted by the light source.
 12. The device of claim 1,further comprising a third layer over the substrate and spaced from thefirst layer and from the second layer, wherein the third layer ispartially optically absorptive, partially optically reflective, andpartially optically transmissive, and wherein the third layer is betweenthe first layer and the second layer.
 13. The device of claim 1, whereinthe first layer has a thickness in the range of 50 to 60 Angstroms. 14.A device comprising; a substrate; first means for partially absorbinglight, partially reflecting light, and partially transmitting light, thefirst means being configured to reflect in a first direction a firstportion of light that is incident on the substrate and transmittedthrough the substrate to the first means; second means for partiallyabsorbing light, partially reflecting light, and partially transmittinglight, the second means being disposed such that the first means isbetween the substrate and the second means, the second means configuredto reflect in the first direction a second portion of light that isincident on the substrate and passes through the substrate and the firstmeans to the second layer; and means for generating light, the lightgenerating means configured to emit a third portion of light through thesubstrate in the first direction and disposed such that the second meansis between the first means and the light generating means, wherein alight emitted from the device in the first direction is of a first colorwhen the light generating means emits the third portion of light and isof a second color when the light generating means does not emit thethird portion of light, the second color being different from the firstcolor.
 15. The device of claim 14, wherein the light generating meanscomprises a light source responsive to a signal and disposed relative tothe substrate such that the first means and the second means are betweenthe light source and the substrate.
 16. The device of claim 14, whereinthe first means comprises a first layer having a thickness in the rangeof 50 to 60 Angstroms.
 17. The device of claim 14, wherein the secondmeans comprises a second layer having a thickness in the range of 30 to300 Angstroms.
 18. The device of claim 14, wherein the first portion oflight and the second portion of light interfere to produce light of acolor that is different than a color of the third portion of light. 19.The device of claim 14, wherein the first means is configured to reflectin a second direction a fourth portion of light that is incident on thesecond means and transmitted through the second means to the firstmeans.
 20. The device of claim 14, wherein the second means isconfigured to reflect in the second direction a fifth portion of lightthat is incident on the second means.
 21. A method of displaying animage, the method comprising: providing a device comprising a substratethat is at least partially optically transparent, a first layer that ispartially optically absorptive, partially optically reflective, andpartially optically transmissive, the first layer being configured toreflect in a first direction a first portion of light that is incidenton the substrate and transmitted through the substrate to the firstlayer, and a second layer disposed such that the first layer is betweenthe substrate and the second layer, the second layer being partiallyoptically absorptive, partially optically reflective, and partiallyoptically transmissive, the second layer configured to reflect in thefirst direction a second portion of light that is incident on thesubstrate and passes through the substrate and the first layer to thesecond layer; emitting from a light source a third portion of lightthrough the substrate in the first direction, wherein the light emittedfrom the device in the first direction is of a first color when thelight source emits the third portion of light and is of a second colorwhen the light source does not emit the third portion of light, thesecond color being different from the first color.
 22. The method ofclaim 28, further comprising sending a signal to the light source, thesignal controlling the emission of the third portion of light from thelight source.
 23. The method of claim 28, wherein the first layer has athickness in the range of 50 to 60 Angstroms.
 24. The method of claim28, wherein the second layer has a thickness in the range of 30 to 300Angstroms.
 25. The device of claim 24, wherein the second layercomprises aluminum.
 26. The device of claim 28, wherein the first layeris configured to reflect in a second direction a fourth portion of lightthat is incident on the second layer and transmitted through the secondlayer to the first layer.
 27. The device of claim 26, wherein the secondlayer is configured to reflect in the second direction a fifth portionof light that is incident on the second layer.
 28. A device comprising:a substrate; an interferometric modulator having a first layerconfigured to reflect in a first direction a first portion of light thatpasses through the substrate and is incident on the first layer and asecond layer configured to reflect in the first direction a secondportion of light that passes through the substrate and is incident onthe second layer, the first layer being between the substrate and thesecond layer; and a light source disposed such that the interferometricmodulator is between the substrate and the light source, the lightsource configured to emit a third portion of light through the substratein the first direction in response to a signal, wherein a light emittedfrom the device in the first direction is of a first color when thelight source emits the third portion of light and is of a second colorwhen the light source does not emit the third portion of light, thesecond color being different from the first color.
 29. The device ofclaim 28, wherein the second layer has a thickness in the range of 30 to300 Angstroms.
 30. The device of claim 29, wherein the second layercomprises aluminum and has a thickness less than 300 Angstroms
 31. Thedevice of claim 28, further comprising a dielectric layer locatedbetween the first layer and the second layer, the dielectric layer atleast partially optically transparent.
 32. The device of claim 28,wherein at least one of the first layer and the second layer isselectively movable so as to change a spacing between the first layerand the second layer.
 33. The device of claim 28, wherein the firstportion of light and the second portion of light interfere to producelight of a color that is different than a color of the third portion oflight.
 34. The device of claim 28, wherein the light source isresponsive to a signal by changing from emitting light of a firstselected color to emitting light of a second selected color that isdifferent than the first selected color.
 35. The device of claim 28,wherein the first layer is configured to reflect in a second direction afourth portion of light that is incident on the second layer andtransmitted through the second layer to the first layer.
 36. The deviceof claim 35, wherein the second layer is configured to reflect in thesecond direction a fifth portion of light that is incident on the secondlayer.
 37. The device of claim 28, further comprising a third layer overthe substrate and spaced from the first layer and from the second layer,wherein the third layer is partially optically absorptive, partiallyoptically reflective, and partially optically transmissive, and whereinthe third layer is between the first layer and the second layer.
 38. Thedevice of claim 28, wherein the first layer has a thickness in the rangeof 50 to 60 Angstroms.